Water-reducing admixtures reduce the amount of water used for fluidifying concrete mixes, and this means that the concrete needs less water to reach a required slump as compared to untreated concrete. A lower water-cement ratio (w/c) can lead to higher strength concrete without increasing the cement amount.
Polycarboxylate (“PC”) type cement dispersants are known for high range water reduction (“HRWR”) whereby water content is reduced by 12-30 percent compared to untreated concrete. HRWR plasticizers are referred to as “superplasticizers” and allow concrete to be highly fluid and to be placed quickly with little or no compaction efforts required.
For example, U.S. Pat. No. 6,187,841 of Tanaka et al. disclosed PC HRWR copolymers having (alkoxy)polyalkylene glycol mono(meth)acrylic ester type monomers and (meth)acrylic acid type monomers. However, this reference emphasizes the need to use large molecular sizes to achieve ideal water reduction conditions. In another example, EP 0 850 894 B1 of Hirata et al. disclosed PC HRWR polymers having polyalkylene glycol ether-based monomers and maleic acid based monomers for achieving high water reducing capabilities, and similarly disclosed molecular size ranges extending upwards to 100,000. Both examples reflect preferences for using a large number of alkylene oxide groups.
In contrast to the extensive polycarboxylate polymer size and weight ranges taught in these exemplary art references, the commercial reality in the concrete industry is that non-PC cement dispersants, such as lignin type plasticizers, are primarily used for low-to-mid-range plasticization of concrete mixes instead of HRWR PC polymers. It appears that polycarboxylate type polymers tend to be reserved for high range water reduction applications, i.e., for achieving the 12 to 30 percent reduction in hydration water that ordinarily would be deployed in HRWR applications.
It is an objective of the present invention to provide an alternative to lignin type water reducers, by achieving low-range and mid-range water reduction in concrete and mortar while using a polycarboxylate type cement dispersant copolymer, and while also achieving greater performance, in terms of admixture dosage efficiency at lower water cuts (i.e., below 12 percent water cut) as compared to conventional (e.g., larger, commercial-scale) polycarboxylate type polymers that are typically used for high range water reduction (HRWR) applications.